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1
2
3 Running Head: Knight et al.: Phenylacetonitrile plus acetic acid to monitor Pandemis
4
5 Use of Phenylacetonitrile Plus Acetic Acid to Monitor
6 Pandemis pyrusana (Lepidoptera: Tortricidae) in Apple
7
8
9 A. L. Knight 1, E. Basoalto 2, G. J. R. Judd 3,
10 R. Hilton 4, D. M. Suckling 5, and A. M. El-Sayed 5
11
12 1Yakima Agricultural Research Laboratory, Agricultural Research Service,
13 USDA, 5230 Konnowac Pass Rd, Wapato, WA 98951
14
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15 ABSTRACT A recent discovery have demonstrated that herbivore induced plant volatile
16 compounds from apple tree infested with leafrollers were highly attractive to con-specific adult
17 male and female leafrollers. However, this work has been conducted in New Zealand and Canada
18 testing only low doses of kairomone. This study has been conducted in US to assess the
19 attractiveness of higher doses of the six apple volatiles provisory identified in apple trees
20 infested by tortricid larvaeto the leafroller, Pandemis pyrusana Kearfott. These volatiles
21 included, β-caryophyllene, germacrene D, benzyl alcohol, phenylacetonitrile, (E)-nerolidol, and
22 indole. No volatiles were attractive to P. pyrusana when used alone. However, traps baited with
23 phenylacetonitrile plus acetic acid caught both sexes of P. pyrusana. Traps baited with the other
24 volatiles plus acetic acid caught zero to only incidental numbers of moths, < 1.0. Adding
25 phenylacetonitrile to traps baited with pear ester, ethyl (E,Z)-2,4-decadienoate plus acetic acid
26 significantly reduced catches of codling moth, Cydia pomonella (L.). However, adding
27 phenylacetonitrile to traps baited with codling moth sex pheromone, pear ester, and acetic acid
28 did not similarly reduce moth catches of C. pomonella. Interestingly, traps baited with
29 phenylacetonitrile plus acetic acid caught significantly more P. pyrusana than traps baited with a
30 commercial sex pheromone lure. The evaporation rate of the acetic acid co-lure was an important
31 factor affecting catches of P. pyrusana with phenylacetonitrile, and studies are needed to
32 optimize the emission rates of both lure components. Further studies are warranted to develop
33 phenylacetonitrile and possibly other aromatic plant volatiles as bisexual lures for the range of
34 tortricid pests attacking horticultural crops.
35 KEY WORDS: codling moth, leafroller, host-plant volatile, benzyl cyanide, benzyl nitrile
36
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37 Pandemis spp. leafrollers are an important group of tortricid pests attacking pome fruits (apple,
38 Malus domestica Borkhausen, and pear, Pyrus communis L.), in North America (Chapman 1973,
39 Dombroskie and Sperling 2012) and in Europe and Asia (Dickler 1991). These species are often
40 bivoltine and overwintering larvae in the fall-spring and summer generations feed on the skin of
41 developing fruits adjacent to leaves creating cull fruits (Brunner 1996). Insecticides are most
42 often used to manage these pests, but sex pheromone mating disruption has been developed and
43 is implemented on a relatively small acreage in North America (Knight and Turner 1999, Judd
44 and Gardiner 2008). Sex pheromone-baited traps are used to monitor adult populations to assess
45 both density and phenology, but pest managers feel they are insensitive to local population
46 densities within the orchards (Brunner 1984). Alternative lures, including acetic acid have been
47 evaluated to monitor both sexes of Pandemis pyrusana Kearfott (Knight, 2001); however, acetic
48 acid alone was considered to be a weak lure and was not adopted by Washington State growers
49 to monitor P. pyrusana (Alway 2003).
50 Several common pome fruit volatiles typically released by healthy or insect-infested fruit
51 and/or foliage in combination with acetic acid have been evaluated as attractants for P. pyrusana
52 and several other key tortricid pests (Knight et al. 2014). Volatiles tested included ethyl (E,Z)-
53 2,4-decadienoate (pear ester), (E)-β-farnesene, (E)-4,8-dimethyl-1,3,7-nonatriene, (Z)-3-hexenyl
54 acetate, and (E,E)-farnesol. Only pear ester and (E,E)-farnesol significantly increased total moth
55 catch (a mix of P. pyrusana and Choristoneura rosaceana (Harris)) when added to traps baited
56 with acetic acid. Subsequently, traps baited with pear ester, (E)-4,8-dimethyl-1,3,7-nonatriene,
57 butyl hexanoate, or (E)-β-ocimene each in binary combination with acetic acid did not catch
58 significantly more P. pyrusana than traps baited with acetic acid alone (Knight et al. 2014).
59 Nevertheless, a novel approach using traps baited with (E,E)-8,10-dodecadien-1-ol, the sex
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60 pheromone of codling moth, Cydia pomonella (L.), pear ester, and acetic acid together was
61 evaluated as a technique to simultaneously monitor codling moth and P. pyrusana (Knight et al.
62 2014). The secondary catch of P. pyrusana in these traps characterized local population densities
63 of P. pyrusana immature stages in commercial orchards more accurately than the industry
64 standard sex pheromone-baited traps. Yet, in general, counts of leafroller adults caught in these
65 traps were low which likely reduces the precision of this approach in estimating local leafroller
66 populations across a range of pest densities. Thus, research has continued to focus on identifying
67 more effective attractants for adult P. pyrusana.
68 Apple seedlings uniquely released several compounds including acetic acid, acetic
69 anhydride, benzyl alcohol, benzyl nitrile, indole, 2-phenylethanol, and (E)-nerolidol only when
70 infested by larvae of light brown apple moth (LBAM), Epiphyas postvittana (Walker), the
71 obliquebanded leafroller (OBLR), Choristoneura rosaceana (Harris) and the eye-spotted bud moth
72 (ESBM), Spilonota ocellana (Denis & Schiffermüller) (Suckling et al. 2012; El-Sayed et al. 2016).
73 Recently El-Sayed et al. (2016) found that binary blend of the two HIPVC, benzyl nitrile + acetic
74 acid and 2-phenylethanol + acetic acid attracted a significant number of conspecific male and
75 female adult LBAM in New Zealand. Further investigation with other leafrollers (Tortricidae) in
76 Canada including the ESBM and OBLR revealed similar systems.. The study reported by El-Sayed
77 et al. 2016 targeted mainly ESBM and OBLR using a lower doses of the new kairomone. In this
78 study we have investigated the response of P. pyrusana to the compounds reported in El-Sayed et
79 al. 2016 using higher doses of the HIPVC in Washington State during 2012-2014.. Also, studies
80 were conducted to evaluate possible interactions with any of the attractive volatiles when combined
81 with pear ester and acetic acid in binary and ternary blends for moth catches of both C. pomonella
82 and P. pyrusana in the same trap.
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83 Materials and Methods
84 Lures. Chemical purity of the volatile apple chemicals used in our trials were as follows:
85 benzyl alcohol (99%), (E)-nerolidol (85%), phenylacetonitrile (99%), indole (99%), β-
86 caryophyllene (97%), and germacrene D (96%) (Sigma Aldrich, St. Louis, MO). These
87 chemicals were loaded (100 mg) into plastic sachet lures. Sachet lures consisted of a heat-sealed,
88 semi-permeable polyethylene bag (45 mm x 50 mm, 150 µm wall thickness), with a piece of
89 cellulose acetate filter (15 mm × 45 mm, Moss Packaging Co. Ltd., Wellington, New Zealand)
90 inserted as the carrier substrate. Two acetic acid (glacial acetic acid (99.7%), Sigma Aldrich) co-
91 lures were made by drilling either 1.0 or 3.2 mm holes in the cap of 8 ml Nalgene vials (Nalg-
92 Nunc International, Rochester, NY) and loading each vial with two small cotton balls and 5 ml
93 of glacial acetic acid. A third acetic acid lure, a proprietary round (3.4 cm diameter) plastic
94 membrane cup (Pherocon AA) was provided by Trécé Inc. (Adair, OK). The mean weekly
95 weight loss (evaporation rate) of acetic acid from the three lures was recorded from 30 August to
96 26 September 2013. Individual lures (N = 10) were placed in red Pherocon VI delta traps (Trécé
97 Inc.) without sticky liners that were hung in the canopy of five linden trees, Tilia cordata Miller,
98 at the Yakima Agricultural Research Laboratory, Wapato, WA. Similarly, the weight loss of
99 sachet lures loaded with phenylacetonitrile (N = 5) was recorded from 28 August to 19
100 September 2013. In addition, the proprietary lures: Pherocon CM-DA lure loaded with pear
101 ester, the Pherocon CM-DA combo lure loaded with codling moth sex pheromone and pear ester,
102 and the Pherocon PLR lure (#3147) loaded with the P. pyrusana sex pheromone were obtained
103 from Trécé Inc.
104 Field experiment protocols. Studies evaluated single, binary, and ternary blends of
105 selected host-plant volatiles and acetic acid co-lures using a standardized protocol in 2012 and
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106 2013. Studies were conducted in two apple orchards, the U.S.D.A. research farm situated east of
107 Moxee, WA (46o30’N, 120o10’W), and in a commercial orchard located southwest of Naches,
108 WA (46o43’N, 120o42’W). Orange delta traps with sticky inserts (Pherocon VI, Trécé Inc.) were
109 used in all studies. Five replicates of each lure treatment were randomized and spaced 20 – 30 m
110 apart. Traps were placed at a 2-m height in the canopy. All lures were placed on the liner. Acetic
111 acid vials with 3.2-mm holes were used in all studies unless specified otherwise. Traps baited
112 with a blank sachet lure were used as a negative control in each study. Studies were repeated a
113 variable number of times and typically each test ran for 5 – 7 d. When studies were repeated on
114 different dates all traps were collected, new lures were transferred to new liners, and traps were
115 re-randomized in the field. Moths were sexed in all studies.
116 Comparison of induced volatiles. Plant volatiles reportedly induced by tortricid larval
117 feeding on apple (El-Sayed et al., 2016) was evaluated in two consecutive studies in the Moxee
118 orchard during 2013. The first study compared moth catches from 12 – 19 August in traps baited
119 with phenylacetonitrile, benzyl alcohol, indole, (E)-nerolidol, β-caryophyllene, or germacrene D;
120 and the combination of phenylacetonitrile with an acetic acid co-lure. The second study
121 compared these same six volatiles all in combination with acetic acid co-lures against acetic acid
122 alone from 19 – 28 August.
123 Combination lures with phenylacetonitrile. Studies conducted in both 2012 and 2013
124 evaluated phenylacetonitrile alone, and in combination with either pear ester or acetic acid, pear
125 ester with acetic acid, and phenylacetonitrile plus pear ester and acetic acid. Traps in 2012 were
126 initially placed in the Moxee orchard on 1 August and traps were checked and re-randomized on
127 8 August. This study was terminated on 13 August and traps were moved to the Naches orchard.
128 Traps were checked and re-randomized in this orchard on 22 and 30 August, and the study was
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129 terminated on 12 September. This same study was repeated in 2013 from 20 – 27 June at both
130 the Moxee and Naches orchards and from 5 - 12 and 17 – 27 August in the Moxee orchard. A
131 third study was conducted from 7 – 21 July 2014 in the Moxee orchard to evaluate the use of
132 phenylacetonitrile with the sex pheromone / pear ester combinational lure and the acetic acid cup
133 lure. A final study was conducted in the Naches orchard from 30 August to 10 September 2014,
134 to compare the magnitude of the total bisexual moth catches of P. pyrusana in traps with
135 phenylacetonitrile plus acetic acid with male catches in traps baited with P. pyrusana sex
136 pheromone.
137 The importance of the acetic acid evaporation rate was evaluated over three time periods
138 in the Moxee orchard during 2013. Traps baited with phenylacetonitrile sachet lures plus acetic
139 acid vials with either 1.0- or 3.2-mm holes or the Pherocon AA cup lure were compared. New
140 lures were used in each of three separate studies which were conducted from 28 August – 4
141 September, 4 – 11 September, and 12 – 19 September, 2013.
142 Statistical analyses. Count data were subjected to a square root transformation prior to
143 analysis of variance (ANOVA) to normalize the variances. A randomized complete block design
144 was used in most studies with date as the blocking variable. Following a significant F-test in the
145 ANOVA, means were separated with Tukey’s HSD test with an alpha value of 0.05. Treatments
146 with zero catches or only incidental catch were not included in these analyses.
147 Results
148 Comparison of induced volatiles. No P. pyrusana were caught with any of the six plant
149 volatiles during test 1 in the Moxee orchard (Table 1). In comparison, small numbers of moths
150 were caught when acetic acid was added as a co-lure to traps baited with phenylacetonitrile
151 (Table 1). During the second test comparing these six volatiles in combination with acetic acid
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152 no moths were caught with β-caryophyllene, germacrene D, or acetic acid alone. Incidental moth
153 catches occurred in blank traps and in traps baited with (E)-nerolidol lures. Means > 1 moth per
154 trap were caught with acetic acid plus either benzyl alcohol, indole or phenylacetonitrile. The
155 bisexual total and female moth catches were significantly greater with acetic acid plus
156 phenylacetonitrile than the other two volatiles plus acetic acid co-lure combinations (Table 1).
157 Combination lures with phenylacetonitrile. Consistent data were collected in both
158 2012 and 2013 when comparing catches of C. pomonella with phenylacetonitrile alone and with
159 binary and ternary blends including pear ester and/or acetic acid (Tables 2 and 3). Pear ester in
160 combination with acetic acid caught significantly more total and female C. pomonella than other
161 lures. Adding phenylacetonitrile to pear ester and acetic acid significantly reduced both total and
162 female moth catches of C. pomonella. Catches of C. pomonella with either phenylacetonitrile
163 alone and in binary blends with either acetic acid or pear ester were low and did not differ
164 significantly. In addition, traps with phenylacetonitrile alone in the 2013 test caught numbers of
165 C. pomonella similar to numbers captured by either acetic acid or pear ester alone. Adding
166 phenylacetonitrile to traps baited with the sex pheromone-pear ester combination lure (Pherocon
167 CM-DA) plus acetic acid did not significantly reduce male, female, or total moth catches in 2014
168 (Fig. 1).
169 Counts of P. pyrusana were more variable in traps than captures of codling moth between
170 both years of the study (Tables 2 and 3). During 2013, traps baited with phenylacetonitrile plus
171 acetic acid or in combination with pear ester caught significantly more total and female moths
172 than all other treatments and did not differ among themselves. However, moth catches in 2012
173 were lower than in 2013 and no significant differences among treatments were found for female
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174 moth catch. Also, total moth catch in traps baited with pear ester plus acetic acid in 2012 was not
175 significantly different from the four treatments that included phenylacetonitrile.
176 The average evaporation rate of acetic acid from the co-lures used with phenylacetonitrile
177 was a significant factor affecting moth catches of P. pyrusana (Table 4). Evaporation rates
178 ranged 18-fold across the three dispensers tested. Moth catches were significantly lower in traps
179 with acetic acid lures with the lowest evaporation rate (plastic cup lure), and did not differ
180 between traps baited with plastic vials with the two different hole sizes. Sachet lures loaded with
181 phenylacetonitrile evaporated an average (SE) of 6.3 (0.2) mg d-1.
182 Moth catches of P. pyrusana in traps placed in the Naches orchard were much higher
183 during 2014 than in the two previous years (Fig. 2). Total moth catch was significantly different
184 and nearly 6-fold higher in traps baited with phenylacetonitrile than with the sex pheromone of
185 P. pyrusana (F 1, 8 = 54.64, P < 0.001). Mean catch of both male (F 1, 8 = 9.30, P < 0.05) and
186 female (F 1, 8 = 20.01, P < 0.01) moths alone were both significantly higher with this binary lure
187 than the catch of males in the sex pheromone-baited traps.
188 Discussion
189 In the studies reported here, phenylacetonitrile and other plant volatiles known to be induced
190 by insect feeding, including benzyl alcohol, indole, and acetic acid provided no intrinsic
191 attraction of P. pyrusana when tested alone. However, when any of the three compounds
192 combined with acetic acid all, and especially phenylacetonitrile, exhibited strong attractiveness
193 to adult male and female P. pyrusana. Benzyl nitrile and acetic acid has been reported as
194 herbivore induced plant volatile in apple as results of LBAM larval feeding, while benzyl nitrile
195 was identified as herbivore induced plant volatile in apple as results of OBLT and ESBM larval
196 feeding (El-Sayed et al., 2016). In our previous work conducted in apple orchards in Canada,
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197 combination of benzyl nitrile and acetic acid or 2-phenylethanol and acetic acid were attractive
198 to adult male and female OBLR and ESBM. The results obtained in this study combined with
199 our earlier results with other tortricids suggest the positive response of adult tortricid to
200 herbivores to HIPV compounds indicate that this is widespread phenomena among these species.
201 Phenylacetonitrile has previously been studied with several tortricids and host-plant material in
202 laboratory studies. For example, phenylacetonitrile was one of 22 compounds identified from the
203 headspace (< 0.5%) of excised peach shoots, Prunus persica L. (Natale et al. 2003), but was not
204 found to be attractive to mated female Grapholita molesta (Busck), when used in a blend with
205 three green leaf volatiles plus benzaldehyde (Piñero and Dorn 2007). Apple leaves also released
206 phenylacetonitrile within a blend of volatiles in response to larval feeding by the tortricids E.
207 postvittana (Suckling et al. 2012) and P. heparana (Giacomuzzi et al. 2013). Yet, neither study
208 measured whether it was attractive to these herbivorous insects.
209 Phenylacetonitrile is a relatively well known semiochemical involved in a range of insect-
210 insect and insect-plant interactions. These include serving as a male-produced anti-aphrodisiac in
211 the butterfly Pieris brassicae L.; facilitating a phoretic dispersal and arrestment by female egg
212 parasitoid Trichogramma brassicae Bezdenko (Fatouros et al. 2005, Huigens et al. 2009); and
213 acting as a male-specific repellant in the locust, Schistocerca gregaria (Forskal) in order to
214 manage sperm competition within insect aggregations (Seidelmann and Ferenz 2002).
215 Phenylacetonitrile is also released by male and female flowers of boxelder trees, Acer negundo
216 L., and it alone attracts nymphs, and both sexes of the adult box elder bug, Boisea rubrolineata
217 (Barber) (Schwarz et al. 2009). Phenylacetonitrile was isolated from oilseed rape, Brassica
218 napus L., and shown to attract cabbage seed weevil, Ceutorhynchus assimilis Payk (Smart and
219 Blight 1997). Similarly, phenylacetonitrile is induced by feeding of the Japanese beetle, Popillia
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220 japonica Newman, and the fall webworm, Hyphantria cunea Drury, on several plant species,
221 including crabapple, Malus sp., and within a blend of induced volatiles, serves as an adult
222 aggregation kairomone (Loughrin et al. 1995). Phenylacetonitrile was shown to be released from
223 cabbage, Brassica spp., and nasturtium, Tropaeolum majus L., following larval feeding of P.
224 brassicae and P. rapae L., but not from undamaged plants (Geervliet et al. 1997). In apple, a
225 significant difference in the release of phenylacetonitrile was found among four cultivars,
226 including, two transgenic scab resistant cultivars (Vogler et al. 2010).
227 Previous studies with plant-feeding Lepidoptera (primarily noctuids and pyralids) have
228 correlated the presence of larval feeding on a host plant with the repulsion of the con-specific
229 adults (Landolt 1993, De Moraes et al. 2001, Signoretti et al. 2012, Reisenman et al. 2013, Zakir
230 et al. 2013, Hatano et al. 2015). No previous studies on tortricid moths have reported whether
231 adults cue to host-plant volatiles induced by larval feeding. When presented alone the induced
232 plant volatiles examined in this study exhibited no attraction to adult P. pyrusana based on the
233 absence of moths in traps. However, we did not study whether these induced volatiles were
234 behaviorally repellent or interfered with volatile-mediated host selection and/or sex pheromone
235 communication (Hatano et al. 2015).
236 Our findings suggest that acetic acid is an important synergist of herbivore-induced plant
237 volatiles for adult P. pyrusana. Interestingly, acetic acid has rarely been reported in the analysis
238 of volatile collections from damaged apple foliage: trace levels were found in samples of cut
239 flowering apple branches (Bengtsson et al. 2001), from apple leaves infested with phytophagous
240 mites (Llusia and Peñuelas 2001), and from drought-stressed trees (Ebel et al. 1995).
241 Interestingly, an earlier paper found phenylacetonitrile was released by spider mite damage on
242 apples (Takabayashi et al. 1994),. Acetic acid is a primary metabolite of plant metabolism under
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243 stress conditions and is regulated by the production and catabolism of ethanol and acetaldehyde
244 (Oikawa and Lerdau 2013). However, acetic acid could also be produced by the growth of yeast
245 and bacteria prevalent in the phyllosphere of apple leaves, or on surfaces of senescent flowers
246 which are relatively rich in sugars and other carbohydrates (Atlas and Bartha 1981, Kinkel
247 1997). A potential role for microorganisms in the herbivore induction of plant volatiles has been
248 suggested previously (Dicke and Hilker 2003, Hilker and Meiners 2006); yet, few studies have
249 tried to measure this interaction. One exception was the purported role of regurgitated
250 endosymbionts in the induction of plant defenses (Spiteller et al. 2000).
251 The interplay of microbial and plant volatiles with an adult tortricid pest has perhaps best
252 been studied with Lobesia botrana (Denis and Schiffermüller) on grapes, Vitis vinifera L., (Tasin
253 et al. 2005, 2011). In this system, neither acetic acid nor the induced volatile 2-phenylethanol
254 was collected from undamaged flowers and fruit (Tasin et al. 2005). However, both compounds
255 were abundant in volatiles from fruit infested with yeasts or acetic bacteria, and both female
256 oviposition and net reproductive rate were significantly increased as a result of microbial
257 infestations of fruit (Tasin et al. 2011). In contrast, fruit infected by Botrytis cinerea (Persoon),
258 did not release acetic acid and was repulsive to females and reduced the overall fitness of the
259 insect. Inoculation of fruit with acetic bacteria produced > 100-fold higher levels of acetic acid
260 than with the yeasts, and oviposition was reduced compared with clean fruit, suggesting an
261 overdose of acetic acid can occur. In our studies, the higher emission rates of acetic acid tested
262 were more attractive, but neither the emission rates of phenylacetonitrile nor acetic acid have
263 been optimized for attraction of P. pyrusana.
264 Our studies can likely impact the pest management of P. pyrusana. Surprisingly, traps baited
265 with phenylacetonitrile and acetic acid caught more moths than sex pheromone traps in an
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266 orchard not treated with leafroller sex pheromones. These data may suggest that the commercial
267 lures for P. pyrusana are not optimized or that other species in the Pandemis limitata
268 (Robinson), group with different sex pheromone blends are more dominant in the two orchards
269 studied (Dombroskie and Sperling 2012). The respective sex pheromones of P. limitata and P.
270 pyrusana have been identified as 91:9 and 94:6 blends of (Z)-11-tetradecenyl acetate and (Z)-9-
271 tetradecenyl acetate (Roelofs et al. 1976, 1977). At least one commercial lure has been reported
272 to be relatively ineffective for P. pyrusana due to contamination with < 1.0% of (Z)-9-dodecenyl
273 acetate (Brunner and Fisher 1998).
274 We found that adding pear ester to traps baited with phenylacetonitrile and acetic acid did not
275 reduce the catch of P. pyrusana. However, adding phenylacetonitrile to traps baited with pear
276 ester and acetic acid significantly reduced catches of C. pomonella. Thus ternary blends in a
277 single trap would be useful in monitoring P. pyrusana, but may compromise catches of C.
278 pomonella. However, a significant drop in catch of C. pomonella did not occur when
279 phenylacetonitrile and acetic acid were added to the combination sex pheromone plus pear ester
280 lure. The potential benefit of improved monitoring of P. pyrusana, especially of female moths,
281 with phenylacetonitrile would have to outweigh the information lost from a drop in catches of
282 female C. pomonella in these combination traps (summarized in Knight et al. 2014).
283 Hypothetically, this could occur in certified-organic orchards if the pest pressure from C.
284 pomonella is low, efficacious tools to manage leafrollers are limited, and especially, when sex
285 pheromone-based mating disruption for leafrollers is used and the standard sex pheromone-
286 baited traps are ineffective. The ability to monitor multiple species could fuel the adoption of
287 labor-saving remote electronic traps (Guarnieri et al. 2011, Kim et al. 2011).
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288 Our positive results with enhancing the bisexual moth catches of P. pyrusana suggest that
289 studies should continue to identify and test other plant volatiles induced by insect feeding on
290 pome fruits (Boevé et al. 1996, Suckling et al. 2012, Giacomuzzi et al. 2013). The use of more
291 complex and ratio-specific blends of induced volatiles should be evaluated, perhaps both alone
292 and in the context of the common volatiles released by uninfested and infested plants (Bruce and
293 Pickett 2011). For example, green leaf volatiles have been found to enhance catches with sex
294 pheromones in field trials with some tortricid pests (Light et al. 1993, Varela et al. 2011, Yu et
295 al. 2015). The release rates of both (Z)-3-hexenyl acetate and (Z)-3-hexenyl benzoate were
296 increased with herbivory (Suckling et al. 2012), and in a previous study, combining (Z)-3-
297 hexenyl acetate with acetic acid nearly doubled the catch of P. pyrusana (Knight et al. 2014).
298 Polyphagous tortricid pests such as P. pyrusana attack a number of horticultural crops other than
299 pome fruits, and future studies should more broadly characterize the induced plant volatiles in
300 these crops to identify other possible attractants, including green leaf volatiles, aromatics,
301 alcohols, and terpenes, and test these in combination with acetic acid as attractive lures.
302
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303 Acknowledgements
304 We would like to thank Duane Larson and Chey Temple, Agricultural Research Service,
305 Wapato, WA for their technical assistance in the laboratory and field. We would like to
306 acknowledge our appreciation to Bill Lingren, Trécé Inc., Adair, OK for donating the
307 commercial lures used in our studies. This project was supported with partial funding from the
308 Washington Tree Fruit Research Commission, Wenatchee, WA.
309
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446 Table 1. Comparison of catches of Pandemis leafroller in traps baited with different host-
447 plant volatiles alone (test 1) or in combination with acetic acid (test 2), N = 5,
448 Moxee, WA, 2013
Mean (SE) catch
Testa Lures b Total Females
1 Blank 0.0 (0.0) 0.0 (0.0)
β-caryophyllene 0.0 (0.0) 0.0 (0.0)
Germacrene D 0.0 (0.0) 0.0 (0.0)
(E)-nerolidol 0.0 (0.0) 0.0 (0.0)
Benzyl alcohol 0.0 (0.0) 0.0 (0.0)
Indole 0.0 (0.0) 0.0 (0.0)
Phenylacetonitrile (PA) 0.0 (0.0) 0.0 (0.0)
PA + acetic acid (AA) 1.6 (0.9) 0.6 (0.4)
2 Blank 0.2 (0.2) 0.2 (0.2)
AA 0.0 (0.0) 0.0 (0.0)
β-caryophyllene + AA 0.0 (0.0) 0.0 (0.0)
Germacrene D + AA 0.0 (0.0) 0.0 (0.0)
(E)-nerolidol + AA 0.4 (0.4) 0.2 (0.2)
Benzyl alcohol + AA 1.0 (0.5)b 0.8 (0.6)ab
Indole + AA 1.0 (0.8)b 0.2 (0.2)b
PA + AA 8.8 (1.6)a 3.2 (1.1)a
ANOVA F 2, 12 = 14.29 F 2, 12 = 4.30
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P < 0.001 P < 0.05
449 Column means for test 2 followed by a different letter were significantly different in a one-way
450 ANOVA, Tukey’s HSD test, P < 0.05.
451 a The first field trial was conducted from 12 – 19 August 2013. The second trial was conducted
452 from 21-28 August, 2013. Due to incidental moth catches only lures in which more than one trap
453 (out of 5) caught > 2 moths were included in the analyses (benzyl alcohol, indole, and PA).
454 b Each plant volatile was loaded on a felt pad in plastic sachets in aliquots of 100 µl. Acetic acid
455 (5 ml) was loaded on cotton balls in plastic vials with a 3.1 mm hole.
456
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457 Table 2. Comparison of catches of codling moth and Pandemis leafroller in orange delta
458 traps unbaited or baited with combinations of phenylacetonitrile, pear ester, and acetic
459 acid, N =10 for codling moth and N= 15 for Pandemis leafroller, Naches, WA 2012
Mean (SE) moth catch per trap b
Codling moth Pandemis leafroller
Luresa Total Females Total Females
Blank 0.2 (0.1) 0.1 (0.1) 0.0 (0.0) 0.0 (0.0)
Phenylacetonitrile (PA) 0.2 (0.2)c 0.0 (0.0)c 0.9 (0.5)b 0.7 (0.5)
Pear ester (PE) + PA 0.7 (0.3)c 0.6 (0.2)c 0.5 (0.2)b 0.3 (0.2)
PE + acetic acid (AA) 15.7 (3.1)a 8.6 (1.4)a 2.2 (0.8)ab 1.2 (0.5)
PA + AA 0.4 (0.2)c 0.2 (0.1)c 4.9 (1.4)a 1.7 (0.6)
PA + PE + AA 5.1 (0.9)b 2.6 (0.6)b 2.6 (1.5)ab 0.7 (0.5)
F 3, 35 = 42.55 F 3, 35 = 34.33 F 4, 68= 4.92 F 4, 68 = 2.03 ANOVAc P < 0.0001 P < 0.0001 P < 0.01 P = 0.10
24 bioRxiv preprint doi: https://doi.org/10.1101/092452; this version posted January 15, 2017. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.
460 Means followed by a different letter were significantly different in a randomized complete block
461 ANOVA, Tukey’s HSD test, P < 0.05
462 a Phenylacetonitrile was loaded on a felt pad in plastic sachets at 100 µl. Pherocon CM DA lures
463 contained 3.0 mg pear ester. Acetic acid (5 ml) was loaded on cotton balls in plastic vials with a
464 3.2 mm hole.
465 b Experiments were repeated on two dates in the Moxee orchard: 1 – 8 and 8 – 13 August.
466 c Data from blank traps for both species and with PA lures for C. pomonella were not included in
467 the analyses.
468
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469 Table 3. Comparison of catches of codling moth and Pandemis leafroller in orange delta
470 traps unbaited or baited with combinations of phenylacetonitrile, pear ester, and acetic
471 acid, N =20, Moxee, WA 2013
Mean (SE) moth catch per trapb
Codling moth Pandemis leafroller
Lures a Total Females Total Females
Blank 0.1 (0.1) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0)
Acetic acid (AA) 0.6 (0.2)bc 0.5 (0.2)bc 0.6 (0.2)b 0.4 (0.2)b
Pear ester (PE) 0.7 (0.2)bc 0.3 (0.2)bc 0.2 (0.1)b 0.1 (0.1)b
Phenylacetonitrile (PA) 0.4 (0.2)bc 0.1 (0.1)bc 0.2 (0.1)b 0.2 (0.1)b
PE + PA 0.6 (0.2)bc 0.1 (0.1)c 0.1 (0.1)b 0.1 (0.1)b
PE + AA 5.2 (1.5)a 2.8 (0.9)a 0.8 (0.2)b 0.4 (0.2)b
PA + AA 0.2 (0.1)c 0.2 (0.1)bc 7.1 (1.6)a 3.8 (1.1)a
PA + PE + AA 1.9 (0.6)b 1.0 (0.3)b 7.8 (1.5)a 4.7 (1.0)a
F 6, 130 = 11.72 F 6, 130 = 9.76 F 6, 130 = 39.84 F 6, 130 = 27.12 ANOVAc P < 0.0001 P < 0.0001 P < 0.0001 P < 0.0001
472 Means followed by a different letter were significantly different in a randomized complete block
473 ANOVA, Tukey’s HSD test, P < 0.05.
474 a Phenylacetonitrile was loaded on a felt pad in plastic sachets at 100 µl. Pherocon CM DA lures
475 contained 3.0 mg pear ester. Acetic acid (5 ml) was loaded on cotton balls in plastic vials with a
476 3.2 mm hole.
26 bioRxiv preprint doi: https://doi.org/10.1101/092452; this version posted January 15, 2017. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.
477 b Experiments were repeated on four orchard-dates: 20 – 27 June in both the Moxee and Naches
478 orchards, and from 5 – 12 and 17 – 27 August in the Moxee orchard.
479 c Data from blank traps were not included in the analyses.
480
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481 Table 4. Comparison of catches of Pandemis leafroller in orange delta traps baited with
482 phenylacetonitrile plus one of three different acetic acid co-lures, N = 15, Moxee WA, 2013.
Type of acetic Mean (SE) daily weight Mean (SE) weekly moth catchb
a acid lure loss (mg) from lure Total Females
Plastic cup 4.9 (0.1)c 10.2 (2.2)b 3.3 (0.8)b
1.0-mm vial 16.1 (2.0)b 26.8 (7.2)a 9.1 (2.4)a
3.2-mm vial 88.6 (3.3)a 17.1 (3.5)a 6.8 (1.4)a
F 2, 27 = 500.8 F 2, 40 = 12.56 F 2, 40 = 10.42 ANOVA P < 0.0001 P < 0.001 P < 0.001
483 Means followed by a different letter were significantly different in a randomized complete block
484 ANOVA, Tukey’s HSD test, P < 0.05.
485 a Acetic acid lures included the proprietary Pherocon AA (Trécé Inc., Adair, OK) plastic cup and
486 polypropylene vials filled with 5 ml of acetic acid and with either 1.0 or 3.2 mm holes.
487 Phenylacetonitrile sachet lures released an average (SE) of 6.3 (0.2) mg d-1.
488 b Experiments were repeated on three dates: 28 August - 4 September, 4 - 11 September and 12 -
489 19 September, 2013 in the Moxee orchard.
490
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491 Footnotes
492 1 Yakima Agricultural Research Laboratory, Agricultural Research Service, USDA, 5230
493 Konnowac Pass Rd, Wapato, WA 98951
494 2 Instituto de Producción y Sanidad Vegetal, Facultad de Ciencias Agrarias, Universidad Austral
495 de Chile, Campus Isla Teja, Valdivia, Chile.
496 3 Agriculture and Agri-Food Canada, Summerland Research and Development Centre,
497 Box 5000, 4200 Highway 97, Summerland, British Columbia, Canada V0H1Z0
498 4 Oregon State University, 530 Hanley Rd., Central Point, OR 97502
499 5 New Zealand Institute for Plant & Food Research Limited, Lincoln, New Zealand.
500
501
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502 Figure Captions
503 Fig. 1. Mean (SE) number of male, female, and total C. pomonella caught in traps with a sex
504 pheromone + pear ester combo lure and an acetic acid co-lure versus these same lures with the
505 addition of a phenylacetonitrile sachet lure, 7 – 21 July 2014, Moxee WA. ‘N.S.’ denotes a
506 nonsignificant difference in moth catches between the two types of lures, P > 0.05.
507
508 Fig. 2. Mean (SE) number of male, female, and total P. pyrusana caught in traps baited with
509 either the sex pheromone lure for P. pyrusana (males only) or with phenylacetonitrile plus an
510 acetic acid co-lure (males, females, and total moths). ‘*’ denotes a significant mean difference
511 with male catch in the sex pheromone-baited trap, P < 0.05.
512
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513
514
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515
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516
33